Telephone ringer



pril 3, 1951 J. R. POWER TELEPHONE RINGER 2 Sheets-Sheet 1 Filed Dec. 22, 1948 MM 1mm.

/Nl EN7'OR By J; RPOWER ATTORNEY 2 Sheets-Sheet 2 J. R. POWER TELEPHONE RINGER FIG. 6

A ril 3, 1951 Filed Dec.

PEEMfl/VENT MAM/V67 ENTOR By JQI OWER Q ATTORNEY Patented Apr. 3, 1951 UNITED STATES rA'rsNT QFEICE- TELEPHONE RINGER James R. Power, Chatham, N. 3., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 22,1948, Serial No. 66,619

' '(Cl. iii-7 6 Claims. 1

This invention relates to electromagnetically operated signaling devices and more particularly to polarized ringers of the type employed extensively at telephone substations.

Since the advent of the combined type of te1ephone set wherein those components of the sub station which were housed previously in a separate container, orbell box, are now housed in the base of the set itself, continuous efforts have been directed to the redesign of such components with a view towards space conservation and an ultimate reduction in the size and weight of the telephone set'without increasing the cost or otherwise limiting the operating capabilities of these components. The component which are now housed in the base of the telephone set include the ringer, its associated" condenser and the induction coil. Of these the telephone ring r has received considerable attention in efforts to arrive at an improved design which would contribute to the attainment of the overall objective of the most economical use of available space and reduction in weight of the combined telephone set. Heretofore, however, considerable difliculty has been encountered in combining smallness of size with improved operating capabilities.

It is the object of this invention to provide an improved type of telephone ringer which is simple in design, compact in construction, small in size, inexpensive to manufacture, susceptible straight line assembly methods and which has operating capabilities exceedin those of ringers in common use today.

This object is attained in accordance with a particular feature of the invention by the utilization of a magnetic circuit of novel configuration which lends itself to the use of a permanent magnet of diminutive size, simple pole-pieces, and

a single coil-bearing laminated core, all combined to effect a small. compact assembly and one which function at maximum efficiency and high sensitivity.

Another feature of the invention resides in the use of a magnetic shunt which is constructed of magnetic iron and is supported on the ringer structure effectively in parallel relation to the, The action of the shunt is to increase the inductance of the ringer coil-bearing laminated core.

client of reducing the noise currents induced in telephone systems? involving grounded ringin circuits.

The shun-t also affords a method. of controlling rent will .be drawn from the telephone line. Also,

this combined impedance is controlled by the resistance component and a. minor reactive component introduced by small departures of the. condenser capacity from nominal value will have little eiiect on the total impedance or on the 016- crating characteristics of the ringer.

At high ringing voltages the shunt may be made to saturate magnetically. This saturation lowers the inductance and thereby throws the ringercondenser combination off resonance at ringing current frequency. This introduces a large reactive component in the impedance of the combination which reduces the ringing current drawn from the line at high voltages.

Still another feature of the invention which contributes materially to the overall objectives bearing core section is a minimum thus permit:

ting the use of a smaller core which results in a saving in core material, in a saving of. copper in the operating winding, and in a reduction in the overall weight and size of the ringer.

,A still further featureof the invention resides" in locating the armature pivot, 61' hinge in alignment with: the polar aXis of the biasing magnet thus rendering negligible the biasing efiect of the magnet on the armature in that area.

These and other features of the invention will be readily understood from the following detailed description when read with reference to the accompanying drawings in which:

Fig. 1 is a front plan view of the ringer embodying the features of the invention;

Fig. 2 is a front .plan View of the ringer shown" in Fig. 1, with the genes removed and the coil indicated in outline in order to show in greater detail the frame, core and other structural details;

Fig. 3 is a side elevation of the ringer structure illustrated in Fig. 2 and shows the relation of the frame, core structure, one leg of the magnetic shunt and motor assembly;

Fig. 4 is another side elevation of the ringer showing the frame, the part of the core structure which passes through the ringer coil and the other leg of the magnetic shunt;

Fig. 5 is an end view of the ringer with the motor assembly removed;

Fig. 6 is a front plan view of the motor assembly;

Fig. 7 includes front and side views of the magnetic shunt; and

Fig. 8 is a, schematic illustration of the magnetic circuit of the ringer and shows the various flux paths set up therein.

The ringer disclosed in the drawings is built around a U-shaped laminated silicon-steel core H0. A coil III is mounted loosely on one leg of the core, that is, on the right leg viewing Fig. 2-. The use of laminated silicon steel for the core reduces the eddy current loss and thereby helps maintain a high inductance at voice frequencies.

A motor assembly H2, shown particularly in Fig. 6 is secured to the lower end of the right leg of core H by means of a screw H3 which passes through suitable holes in the core laminations and accommodates a suitable nut, not shown. The motor assembly includes a U- shaped magnetic iron pole-piece H having two inwardly (Fig. 2) projecting legs H6 and Hi, the latter of which projects downwardly to ef fect an extension H8. The leg H6 of this polepiece forms the pole face of one of the operating magnetic gaps. To the leg extension H8 there is fixed, preferably by welding, a small bar-type permanent magnet H9 of substantially square section. Modern magnetic alloys of high coercive force make feasible the use of a very short magnet located as described. A magnetic iron yoke I is fixed to the other end of the magnet H9, preferably by welding and is characterized by two bent-over, oppositely disposed arms I2I which are provided with suitable c0- axial holes to accommodate, by a drive fit, a pivot pin I22.

A substantially rectangularly-shaped armature I23 is provided with integral bent-over sections I24 and I25 having suitable holes which accommodate the pivot pin I22 in a manner to per-- mit the armature to rotate freely about the pin. Two stops I26 and I2! (Fig. 6) are riveted to the armature near its outer end. These stops limit the motion of the armature by striking the pole faces H6 and I36, respectively. The location of the operating gaps close to the end of the magnet results in a minimum magnetic leakage and thereby reduces the required size of the magnet.

An integral arm I28 formed on the armature extension I24 serves to support a clapper rod I29 which is staked therein. A yoke-shaped clapper I30 is staked to the other end of the clapper rod. Two projections I3I of this yoke are disposed to strike the inside surfaces of gongs I49, an arrangement which permits a closer mounting of the gongs than is possible with the usual type of clapper and which therefore results in a reduction in the overall size of the ringer.

A biasing spring I32 is also staked 0 h turned-up portion I28 of the armature, the free end of which may be selectively engaged in one of several notches in the edge of a plate I33 fastened to section H1 of pole-piece H5. The biasing spring is so shaped that when engaged in any of the notches it will exert a force on the armature tending to hold the stop I21 against pole face I36. The magnitude of this force is adjustable by the selection of the notch in which the spring is engaged.

A second magnetic iron pole-piece I34 is fastened to the exposed leg of core H0 by means of rivets I35. A bent-down section of this polepiece forms the pole face I36 (mentioned hereinbefore) of the operating magnetic gap.

The space between the pole faces H6 and I36 is adjusted to provide the desired air-gap in the magnetic circuit. The armature I23 normally is positioned in this gap by the stop I 2'! which is forced against the pole face I36 by the tension of the biasing spring I32. The length of the stop I2? is such as to hold the armature substantially in the magnetic neutral of the gap when there is no current flowing in the operating coil III. The length of the other stop I26 is designed to limit the movement of the armature to a predetermined extent. Pole face H6 is slightly skewed so that it is parallel to the armature in the operated position, that is when stop I26 is in contact with pole face I I6.

A U-shaped magnetic shunt I38 (Fig. 7) of magnetic iron is secured to the outer leg of core I I 0 by means of a screw I31 which passes through suitable holes in the shunt and in the core laminations and is screwed into the pole-piece I34. The end of the other opposite leg of the shunt is held in contiguous engagement with the bottom of the inner leg of the core by means of a screw H3 and a nut H4 which also secure the pole-piece H5 to the core. A section of the shunt I38 is fashioned at 99 (Fig. 3) so as to clear the pole faces H6 and I36. The crosssection of this shunt is proportioned so that it will become magnetically saturated at a predetermined value of ringing current as will be described in detail hereinafter. In Figs. 2, 3 and. 4 the several integral sections of the shunt are designated I38, I38a, I381) and I 380. These designations are also employed in Fig. 7.

A mounting bracket I 39 is secured to section I38a of the magnetic shunt by means of a rivet I46 (Fig. 5) and a screw MI and its associated nut I42. This bracket has a notch I43 in its outer edge designed to engage a resiliently-mounted stud (not shown) in the base of a telephone set. The bracket I 39 also has a hole I44 through which the left end (viewing Fig. 3) of pivot pin I22 projects. This latter aids in locating the motor assembly H2- and prevents rotational displacement about the screw H3. A mounting bracket I45 is secured to the closed end of the core III) by means of a rivet I35 and a screw I46 and its nut I41. Two upwardly extending arms I48 of the bracket I45 provide supports for gongs I49. The axes of the gongs are held at an angle of approximately 45 degrees with respect to the plane of the core II 6 and to the clapper rod I 29. This angle results in a more compact arrangement than would be possible if the axes of the gongs were parallel to the clapper rod. The gongs are secured to the bracket arms I48 by means of screws I50 which pass through eccentrically-located holes in the gongs and are threaded or screwed into suitably tapped holes in bracket extensions I 5I. The position of the of each gong relativeto the clapper Ice is adjustable by rotation of the gong about its eccentr l y locate'd mounting hole. The bracket- [45 is also provided with a notch I52 for engagemeat with another; stud (not shown) in the base of the telephone set and with a threaded hole- PS3 to receive a screw that passes through an eyelet (not shown) in the base of the set. The ringer is thus held in place by means of the two notches M3 and IE2. and the screw that fits into the hole. I53;

Fig. 8 illustrates, diagrammatically, the mag net fiu x'i paths in the magnetic system embodied the ring-er of this invention. The biasing flux path, that is, the path traversed by the flux set up by the permanent magnet H9. is represented by continuous lines while the path of the flux set up by the ringing current is represented by a broken line. The arrowheads on the continuous lines indicate thedirection of the biasing flux. in the circuit at all timeswhile the arrow heads on the broken lines indicate the direction. of the ringing current flux during one-half cycle of current, it being understood that the flux di rection in the latter case is reversed every half cycle. The magnetic shunt inthis figure is represented, for simplicity, by a straight-bar interconnecting. the opposite legs of the ringer core.

The permanentmagnet flux emanating from the north pole N of the permanent magnet H9 enters section N8 of the pole-piece H5 and on leaving it, traverses three parallel branches one of which includes section H5, air-gap a. armature m and back to the south pole S of the magnet M9 by way of air-gap another by way of the magnetic iron shunt I38, air-gap b, armature I23 and thence back to the permanent magnet M9 by way of air-gap c; and a third path which includes the core H0 in place of the shunt I38 in the second path traced.

When the armature I23 is near the center of the air-gap in which it operates the total effect of the biasing fluxes in gaps a and b is small since they are substantially eoual in magnitu eand directionally opposed relative to their effect ,on the armature. The flux in gap b tends to pull the armature I 23 towards the pole 136 while the flux in gap a tends to pull the armature towards the other pole H6. Hence, in so far as the biasing flux in gaps a and b is concerned the armature I2 3 issubstantially balanced. The pivot point about which armature 123- is adapted to rotate is, in accordance with a particular feature of the invention, intentionally located in alignment with the polar axis of the permanent magnet H9 in order that the ma netic force in gap 0 will not contribute materially to the magnetic bias.

When ringing current traverses the coil HI the first half cycle causes flux to flow downward in the core H0 whence it divides, part of it being additive to the biasing flux in shunt I38 and another part being additive to the biasing in secon. H and air-gap a, and opposed to the biasing flux in airgap b and the other leg of the core. Under this condition the total flux in gap a predominates to an extent such that the unbalance in the magnetic forces overcomes the force of thebiasing spring 132-. The armature then moves clockwise about its pivot. As the armature moves, the length of gap a decreases and that of gap 1) increases causing a redistribution of the polarizing flux such that the force of gap a due to the polarizing flux increases and the force in gap 11 due to the polarizing flux decreases. The armature I23 thus moves until the stop I26 engages the pole face H5 and the clapper 1 3i strikes one of the gongs- M9. on the other half cycle of ringing current the described conditions of the flux due to the ringing current are reversed and the ringing current flux is additive to the polarizing flux in gap 12' and opposes it in gap a. The change in total flux caused by this half cycle of ringing 1 current thus assists the biasing spring I32 in moving the armature I23 in a counter-clockwise direction, that is, from its operated position in which the stop I26 contacts pole face HES to its non-operated position in which the stop I21 contacts pole face I36, The overthrow of the clapper rod on this return movement of the armature results in the actuation of the other gong I49.

It will be noted that during the first half cycle of ringing current which results in armature I23 being moved out of its non-operated position, the ringing current flux in the core HE! is directively opposed to the polarizing flu-x therein so that the total flux in the coil-bearing core section I It is less than the ringing current flux. Of course, during the next half cycle the ringing current flux and the biasing flux are additive and the total flux in this portion of the core is greater than the ringing current flux, but, as will be described presently the magnetic action during the first half cycle of ringing current is of relatively greater importance.

The ringer of this invention is arranged so that as the armature I23 moves from its non-operated position to its operated position energy is stored in biasing spring 132. When the ringing current falls to? zero the energy in the biasing spring is sufficient to return the armature to its non-operaed position and to cause one of the gongs [49 to be s ruck by the clapper I556. Obviously, current flowing inthe opposite direction also will tend to move the armature from its operated position to its non-operated position but the restoration of the armature is not de endent u on current flow. Thus it is apparent, particularly at current values near the minimum capable of operating the ringer that the basic problem involved in the design of the magnetic system of a telephone ringer is embodied in the movement of the armature out ofits non-operaed pos tion, the reverse motion of the armature being achieved substantially mechanically.

With the arrangement employed in the present ringer in which the biasing flux cancels a significant part of the ringing current fluxin the core section H) during the half cycles of ringing current associated with the movement of the armature from its non-operated position to its operated position there is a relatively small amount of flux flowing through the core during the time when it is desired that the ringing current exert the greatest force upon the armatare.- This smaller quantity of flux which flows through the core when the ringer produces its maximumeffort permits the use of a smaller core with an attendant saving in core material and in copper in the operating winding, and results in a reduction in the overall weight and size of the ringer. Also this reduction in flux reduces the loss of magnetomotive force at the contacting surfaces between the core ends and the polepieces. quirements on the reluctance of these contact areas.

While it is apparent that the combination of This is desirable as it relaxes the refiuxes in those sections of the magnetic circuit external to the coil-bearing core section is the converse of that in the coil-bearing section and that, therefore, during the above-indicated half cycles of ringing current, the total flux will exceed the ringing current flux thus suggesting a necessary increase in the amount of material in these sections, it is to be observed that none of these sections is located within the coil and, therefore, can be made as large as necessary without having the effect upon the size and cost of the ringer that would result from the enlargement of the coil-bearing core section I i0.

What is claimed is:

1. A telephone ringer comprising, in combination, a U-shaped laminated core, a coil mounted on one of the opposed legs of said core, a polepiece of magnetic iron fixed to each opposed core leg near its end to effect an air-gap, a pivotallymounted armature disposed for operation in said air-gap, and a straight bar-type permanent magnet having its polar and longitudinal axes coincident, said magnet having one end in fixed abutting relation to one of said pole-pieces and projecting therefrom in a direction such that the pivot mounting for said armature is located on the polar axis of said magnet.

2. In a telephone ringer, a laminated U-shaped core, a coil mounted on one of the opposed legs of said core, pole-pieces fixed to the ends of said core legs effecting an air-gap, an armature disposed in said air-gap for operation therein incident to the energization of said coil by alternating current, mechanical means for biasing said armature in the direction of one of said polepieces, a straight bar-type permanent magnet disposed relative to said core and said polepieces so that when said coil is traversed by half cycles of current which cause said armature to move in the direction of the other of said polepieces the flux in the coil-mounting leg of said core produced by the said half cycles of current is directively opposed by flux set up in the said coil-mounting core leg by said permanent magnet, and means mounting said armature for pivotal movement about a line coincident with the polar and longitudinal axes of said magnet.

3. In a telephone ringer, a, laminated U-shaped core, a coil mounted on one of the opposed legs of said core, a pole-piece fixed to each opposed leg of said core to effect an air-gap therebetween, a straight bar-type permanent magnet fixed at one end to an extension of one of said polepieces with its polar and longitudinal axes coincident and at right angles to the longitudinal axes of the opposed core legs, a pivot pin supported by the other end of said permanent magnet and located in the plane of the polar axis thereof, and an armature mounted on said pivot pin for oscillatory movement in said air-gap.

4. In a telephone ringer, a laminated U-shaped core, a coil mounted on one of the opposed legs of said core, a pole-piece fixed t the end of each opposed leg of said core and efiecting an air-gap therebetween, a bar-type permanent magnet 8 fixed atone end to one of said pole-pieces with its polar axis at right angles to the longitudinal axes of said core legs, an armature supported on the other end of said permanent magnet for pivotal movement about the polar axis thereofand for oscillation in said air-gap, and a shunt of magnetic iron coupling the ends of the 0pposed legs of said core.

5. In a telephone ringer, a U-shaped core, pole-pieces fixed to the ends of said core to effect an air-gap, a straight bar-type permanent magnet for producing a biasing flux in said air-gap having its polar and longitudinal axes coincident, an armature having but one end disposed in said air-gap and the other end in spaced relation to one end of said permanent magnet, whereby said armature and the spacing between the armature and permanent magnet provide a return path for the biasing flux traversing the said air-gap, and means for mountin said armature for pivotal movement about the polar axis of said permanent magnet whereby the biasing effect of the flux traversing the spacing between the armature and the permanent magnet is substantially nil.

6. In a telephone ringer, a magnetic circuit including a core comprising U-shaped silicon-' steel laminations, a soft iron pole-piece fixed to one of the opposed legs of said core and having a downturned integral portion effecting a pole face, a U-shaped soft iron pole-piece fixed at the end of the other of the opposed legs of said core, one of the opposite legs of which eiTects 'a second pole face located in juxtaposition to the other pole face, and the other leg of which is extended in a plane parallel to the plane of said core, a substantially U-shaped shunt of magnetic iron having each of its two opposed legs in contiguous relation to a different one of the two opposed legs of said core and its bridging piece disposed between the ends thereof, a bar-type permanent magnet fixed at one end to the extended leg of said U-shaped pole-piece and projecting therefrom at right angles in the direction of the air-gap effected by the pole faces of said pole-pieces, a plate fixed to the other end of said permanent magnet and having a pair of oppositely disposed projections located in the plane of the polar axis of said permanent magnet, a mounting pin supported between said plate projections, and an armature mounted for rotation on said pin and extending therefrom into the airgap effected by the pole faces of said pole-pieces.

JAMES R. POWER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

